Microbe

The human gastrointestinal tract is not only crucial for the digestion of food and utilization of nutrients, but it is also inhabited by a complex ecosystem of trillions of microbes, which together comprise an important part of the gastro-intestinal ecosystem. Microbial abundance is highest in the colon, making it the habitat for more than 70 % of the microbes living in and on the human body (1). There are high interindividual differences in microbiota composition – comparable to the individuality of a fingerprint (2). Factors that influence composition and contribute to the uniquity include mode of birth, age, diet, geography, exercise, pharmaceutics/antibiotics and genetics (3).

The consequence of the microbial richness is a vast gene set which is about 150 times the size of the human genome (4,5). By expressing genes that are not represented in humans, our gut microbiota owns structural and protective functions, as well as essential metabolic functions. For instance, it plays a crucial role in intestinal barrier function, immune system development and function, displacement of detrimental microbes and furthermore produces antimicrobial factors which protect us from pathogens and toxins (6). In addition, our gut microbiota can also generate signaling molecules, such as short chain fatty acids or neurotransmitters (e.g. serotonin or γ-Aminobutyric acid). These molecules can affect the function of our immune system, the metabolism, and the enteric nervous system/the vagus nerve, thus establishing a link to the brain. This connection is referred to as microbiota-gut-brain axis (7).

At NGBI we investigate gut microbiota composition in many of our intervention studies and evaluate its functionality via 16S rRNA, metagenomics and metabolomics analysis. Additionally, we have the possibility to conduct in vitro faecal fermentation experiments to assess the metabolization of different food components or chemical substances (e.g., persistent organic pollutants) by the human gut microbiota.

In our studies applying faecal microbiota transplantation (FMT) – which includes the transfer of a specific composition of microbes – it was observed that FMT affected the mucosal gene expression related to immune response and metabolism in irritable bowel syndrome patients, and improved symptoms in a subset of collagenous colitis patients (8,9).

Additionally, we focus on the connection between microbiota and brain function. For instance, our intervention study using a probiotic mixture found altered brain responses in regions involved in emotional, cognitive and face processing in comparison to a placebo group (10).

We are very active in investigating the potential health effects of probiotics in various target groups. Just recently, we investigated the effect of probiotics on the immune system – more precisely the antibody response after a SARS-CoV-2 infection (11).